From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DECE1C32750 for ; Wed, 14 Aug 2019 00:07:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDB5020843 for ; Wed, 14 Aug 2019 00:07:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726755AbfHNAHT (ORCPT ); Tue, 13 Aug 2019 20:07:19 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:35470 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726102AbfHNAHT (ORCPT ); Tue, 13 Aug 2019 20:07:19 -0400 Received: from callcc.thunk.org (guestnat-104-133-9-109.corp.google.com [104.133.9.109] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x7E06OWr006647 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 13 Aug 2019 20:06:26 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 2267D4218EF; Tue, 13 Aug 2019 20:06:23 -0400 (EDT) Date: Tue, 13 Aug 2019 20:06:23 -0400 From: "Theodore Y. Ts'o" To: Linus Torvalds Cc: Arnd Bergmann , Linux Kernel Mailing List , Thomas Gleixner , John Stultz , Alexandre Belloni , Stephen Boyd , Florian Weimer , "H. Peter Anvin" , Palmer Dabbelt , Alistair Francis , GNU C Library , Karel Zak , Lennart Poettering , OGAWA Hirofumi Subject: Re: New kernel interface for sys_tz and timewarp? Message-ID: <20190814000622.GB20365@mit.edu> Mail-Followup-To: "Theodore Y. Ts'o" , Linus Torvalds , Arnd Bergmann , Linux Kernel Mailing List , Thomas Gleixner , John Stultz , Alexandre Belloni , Stephen Boyd , Florian Weimer , "H. Peter Anvin" , Palmer Dabbelt , Alistair Francis , GNU C Library , Karel Zak , Lennart Poettering , OGAWA Hirofumi References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 13, 2019 at 10:30:34AM -0700, Linus Torvalds wrote: > > I suspect the only actual _valid_ use in the kernel for a time zone > setting is likely for RTC clock setting, but even that isn't really > "global", as much as "per RTC". As I recall (and I may or may not have been original for the original sys_tz; it was many years ago, and my memories of 1992 are a bit fuzzy) the only reason why we added it was because x86 systems that were dual-booting with Windows had a RTC which ticked localtime, and originally, the system time was fetched from the RTC in early boot, and then when the timezone was set, the time would be warped so it would be correct. Trying to use this for anything else is probably a bad idea, and in a world where we can have initrd's and reading the RTC gets done by userspace as opposed to kernel, it probably doesn't make any sence to keep it. Cheers, - Ted